This invention relates to illumination systems for jet drop copiers and duplicators of the type disclosed and claimed in copending application Ser. No. 75,063, filed Sept. 12, 1979.
Prior art illumination systems for jet drop copying have used fixed sources of illumination, as generally disclosed in Paranjpe et al U.S. Pat. No. 4,112,469. Such prior art illumination systems flood the original document with a constant field of uniform light. This wastes energy, because only relatively small portions of the document are being viewed at any one time by the image scanning system. Moreover, the prior art system is unable to provide illumination at sufficiently high levels for document scanning at the speeds contemplated by Ser. No. 75,063.
Another prior art illumination arrangement for ink jet copying is disclosed in Taylor U.S. Pat. No. 3,564,120, wherein a series of sensing heads each contain a light source and a photosensing element. The light sources create small spots of illumination, which are swept across the document by the scanning heads.
Other illumination arrangements within the general field of flat plane document scanning are disclosed in Herriott U.S. Pat. No. 2,262,584 and Lloyd U.S. Pat. No. 3,752,558. Herriott discloses means for scanning a beam of light, while Lloyd discloses a moving carriage upon which are mounted a series of illuminating lamps.
Another prior art arrangement, as disclosed in Libby U.S. Pat. No. 3,694,070, utilizes a pair of rotating reflectors for synchronous scanning of elongated light beams across the surface of a document positioned on a curved document plane.